1. Technical Field
The present invention is directed to a positioning system and method using a data communication network. If a positioning device transfers primitive GNSS digital data from GNSS satellites (e.g., intermediate frequency or baseband digital data) and additional information required for enhanced performance (e.g., timing information, cell-based information, bit data and carrier frequency shift information for each satellite) to a location tracking server by using a data network, the location tracking server calculates a position of the positioning device by enhancing receiver sensitivity utilizing plentiful computation power which is not realistic in the ordinary GNSS positioning devices. Thus, the positioning device may find its location even in very poor signal condition (e.g., the inside of a room or where the signal from GNSS satellites is severely attenuated). Such a GNSS-based positioning system may be applied to various location-based services.
Further, the present invention is directed to a positioning system and method using a data communication network, which may achieve time synchronization when there is a need to extract not only position information but also absolute timing information.
2. Description of Related Art
A global navigation satellite system (GNSS) is the standard generic term for satellite navigation systems that provide autonomous geo-spatial positioning with global coverage, which may include global positioning system (GPS), GLONASS, Galileo, Compass, etc. GPS is a GNSS developed and operated by the U.S. Department of Defense. In the case where a GPS is used, a GPS receiver receives a signal from 24 satellites orbiting the earth twice a day. Generally, a GPS receiver detects more than four satellite signals and it may find a location (longitude, latitude, and altitude) of the receiver with a series of signal processing operations.
In recent years, the usage of GNSS has been increased and extends to non-military (civilian) applications from its original military purposes. Moreover, applications of GNSS are spreading to wireless navigation systems and so forth. GPS has been widely used in not only simple wireless navigation systems but also location-based services. The Federal Communications Commission (FCC) enacted a compulsory regulation to identify a caller's location in an emergency call (911) to a communication carrier. Therefore, a positioning system using GNSS has become an essential, not auxiliary system.
A GNSS receiver continues to advance in performance. A terminal equipped with a GNSS receiver has no problem in identifying its location for the obstacle-free outdoor environments. However, when the signal strength from GNSS satellites is severely attenuated (e.g., for indoor or urban canyon environments), its location cannot be easily found by means of a conventional GNSS receiver.
Various location-based services are required to work in the indoor environment as well as in the outdoor environment. Especially an emergency situation, where the emergency user's position should be found, may happen at inside room or an area where the signal from GNSS satellites is heavily attenuated. Thus, the improvement of a GNSS-based positioning performance is required for various and advanced location-based services such as disaster or rescue services.
Various techniques have been developed to improve the performance of a GNSS receiver. However, it is very hard to improve the receiver sensitivity of a terminal by itself. That is, there is still a limitation in improving the performance of a GNSS receiver. Nonetheless, there are requirements for enhanced performance of the positioning technique.
GNSS has been popularly used to identify and track a location of a terminal. When three or four satellite signals from GNSS satellites are possible to be detected, a GNSS receiver may find a location of the terminal.
However, as set forth above, when a conventional GNSS receiver is located at inside room or an area where a signal from a GNSS satellite is heavily attenuated, it is difficult that the conventional GPS receiver detects three or four satellite signals at the same time. Thus, the location cannot be identified and tracked. In various location-based services, especially under an emergency or disaster situation, a GNSS-based positioning device is required to work even at an area where the received signal strength is very weak. Hence, the enhancement of the receiver sensitivity at a GNSS receiver is increasingly required in various and advanced location-based services.